Temperatures have increased around the globe, affecting many ecosystems, including high-elevation Andean streams where important aquatic insect species coexist. Depending on the magnitude of change, ...warming could lead to the mortality of sensitive species, and those tolerant to rising water temperatures may exhibit differences in growth rates and development. Taxon-specific optimal temperature ranges for growth determine how high or low temperatures alter an organism's body size. In this study, we observed the effects of different climate change scenarios (following three scenarios of the 2021 IPCC predictions) in two aquatic insect species distributed in high-elevation streams in Ecuador: the mayfly Andesiops peruvianus (Ephemeroptera: Baetidae) and the caddisfly Anomalocosmoecus illiesi (Trichoptera: Limnephilidae). We assessed how increased water temperatures affect larval growth rates and mortality during a 10-day microcosm experiment. Our results showed that Andesiops peruvianus was more thermally sensitive than Anomalocosmoecus illiesi. Mortality was higher (more than 50% of the individuals) in mayflies than in caddisflies, which presented mortality below 12% at +2.5°C and +5°C. Mortality in mayflies was related to lower dissolved oxygen levels in increased temperature chambers. Higher temperatures affected body size and dry mass with a faster growth rate of Andesiops peruvianus larvae at experimentally higher temperatures, suggesting an important response of this hemimetabolous species to stream temperatures. For Anomalocosmoecus illiesi, we did not find significant changes in mortality, body size or growth rate in response to temperature changes during our experiment. In situ outcomes of species survival and growth in Andean streams are difficult to predict. Nevertheless, our results suggest that at only +2.5°C, a water temperature increase affected the two insect taxa differentially, leading to a drastic outcome for one species' larvae while selecting for a more tolerant species. Our study suggests that climate change might produce significant mortality and growth rate effects on ectotherm tropical aquatic insects, especially Andean mayflies, which showed higher sensitivity to increased water temperature scenarios.
Species richness is greatest in the tropics, and much of this diversity is concentrated in mountains. Janzen proposed that reduced seasonal temperature variation selects for narrower thermal ...tolerances and limited dispersal along tropical elevation gradients Janzen DH (1967) Am Nat 101:233–249. These locally adapted traits should, in turn, promote reproductive isolation and higher speciation rates in tropical mountains compared with temperate ones. Here, we show that tropical and temperate montane stream insects have diverged in thermal tolerance and dispersal capacity, two key traits that are drivers of isolation in montane populations. Tropical species in each of three insect clades have markedly narrower thermal tolerances and lower dispersal than temperate species, resulting in significantly greater population divergence, higher cryptic diversity, higher tropical speciation rates, and greater accumulation of species over time. Our study also indicates that tropical montane species, with narrower thermal tolerance and reduced dispersal ability, will be especially vulnerable to rapid climate change.
Rhyacoglanis pulcher is a rare Neotropical rheophilic bumblebee catfish known only from the type locality in the Cis-Andean Amazon region, Ecuador, and the type-species of the genus. So far, the ...three syntypes collected in 1880 were the only specimens unambiguously associated to the name R. pulcher available in scientific collections. Recently, a specimen was discovered in a fast-flowing stretch of the Villano river, a tributary of the Curaray river, Napo river basin, Ecuador, representing a new record after nearly 140 years. Here, we present this new record, identified by morphology, provide the DNA barcode sequence of the specimen, and propose why the species of Rhyacoglanis are scarce in zoological collections. Additionally, we discuss the intraspecific variation in the color pattern observed in R. pulcher.
Andes-to-Amazon river connectivity controls numerous natural and human systems in the greater Amazon. However, it is being rapidly altered by a wave of new hydropower development, the impacts of ...which have been previously underestimated. We document 142 dams existing or under construction and 160 proposed dams for rivers draining the Andean headwaters of the Amazon. Existing dams have fragmented the tributary networks of six of eight major Andean Amazon river basins. Proposed dams could result in significant losses in river connectivity in river mainstems of five of eight major systems-the Napo, Marañón, Ucayali, Beni, and Mamoré. With a newly reported 671 freshwater fish species inhabiting the Andean headwaters of the Amazon (>500 m), dams threaten previously unrecognized biodiversity, particularly among endemic and migratory species. Because Andean rivers contribute most of the sediment in the mainstem Amazon, losses in river connectivity translate to drastic alteration of river channel and floodplain geomorphology and associated ecosystem services.
Summary
Glaciers that directly feed high‐altitude streams create unique environmental conditions that contribute substantially to regional‐scale lotic habitat diversity and biodiversity, including ...intra‐specific genetic diversity (as population structure) between glacier‐fed and other types of streams (e.g. groundwater‐fed). However, these population‐genetic patterns are thus far only understood for macroinvertebrates in the temperate zone, where strong seasonality and narrow temporal windows for emergence and mating could help drive patterns of genetic differentiation between streams with contrasting temperature, flow, or other environmental characteristics influencing life‐history patterns.
Our primary objective was to assess population‐genetic structure between groundwater‐(GW) and glacier runoff‐fed (RO) streams in high‐altitude tropical (relatively aseasonal) basins of the Ecuadorian Andes. Our focal species was Andesiops peruvianus, a baetid mayfly confamilial with well‐studied temperate alpine mayflies. We pursued secondary objectives of evaluating broader scale population‐genetic patterns across mountain ranges for the first time in high‐altitude tropical streams, and evaluating genetic evidence for recovery from population bottlenecks in this volcanically active region.
For the primary objective, we collected A. peruvianus (mean N = 16.5 per reach) and a suite of environmental variables from six intra‐basin pairs of GW/RO stream reaches at altitudes 4000–4300 m a.s.l. on three glaciated volcanoes representing two parallel sub‐ranges of the Ecuadorian Andes. We tested for significant GW/RO pairwise differences in haplotype distribution and genetic diversity obtained by sequencing the barcoding region of the mitochondrial cytochrome oxidase I gene. For the broader scale sub‐objectives, we added two unpaired populations (total N = 231) and evaluated genetic structure at nested spatial scales of streams/basins/mountains, and we tested for differences between mountains. We also measured Tajima's D and Fu's FS to evaluate evidence for demographic instability at the scale of individual mountains, each with a different volcanic history.
We found no evidence for population structure between GW and RO streams within basins. Population structure among basins within mountains was significant, but only in areas where streams occupied deep, physically isolating canyons. Comparisons between all possible pairs of the three mountains revealed significant structure, but pairwise ΦST was an order of magnitude greater between pairs of mountains occupying different ranges than for the pair in the same range. Indeed, no haplotypes were shared between the two Andean sub‐ranges. All three mountains, regardless of recent volcanic history, showed a significant signature of recovery from recent bottleneck.
Our results suggest that strong environmental differences between glacial runoff and groundwater stream types do not isolate these tropical, high‐altitude mayfly populations. Rather, populations are panmictic within basins. Broader scale patterns among mountains suggest that dispersal and gene flow in these tropical streams proceed similarly to temperate alpine systems; that is, relatively strong isolation among mountains but reasonable capacity for gene flow between headwaters in close proximity on a single mountain. A notable difference from the temperate studies is that mayfly populations in Ecuadorian high‐altitude streams appear to be demographically unstable, regardless of the recent volcanic eruption history of the mountain they occupy. Frequent eruptions in this volatile region might affect streams across areas more extensive than a single mountain.
Climate change and nutrient enrichment are two main stressors of rivers in Andean ecosystems. As temperatures increase globally, species are expected to be affected in various ways, including growth ...and survival. Here, we performed a novel, 15-day microcosm experiment to test the impact of multiple stressors on algae biomass (measured as chlorophyll-
a
biomass), the main food supply of two aquatic insect grazers, and its effect on their survival and growth rates. We used
Andesiops peruvianus
(Ephemeroptera) and
Anomalocosmoecus illiesi
(Trichoptera), two abundant species in Andean rivers in Ecuador. The experiment tested the addition of nitrogen (N) and phosphorus (P) using nutrient-diffusing substrates (NDS) in three Intergovernmental Panel on Climate Change (IPCC) temperature scenarios (ambient, +2.5 °C, and +5 °C). The single effect of increasing temperature produced an increase in algal biomass. Positive synergistic effects on chlorophyll-
a
biomass resulted in ambient chambers with a mix of N+P addition and a combination of +2.5 °C with +P and N+P. The single and interactive effects of nutrient addition and warming water produced high mortality for
Andesiops peruvianus
but did not impact the survival of
Anomalocosmoecus illiesi
larvae. The growth rates of
Andesiops peruvianus
larvae showed no significant effect in any treatments except for the ambient NP treatment, in which we observed a marginal impact on body mass. In turn, the growth rates of
Anomalocosmoecus illiesi
larvae increased significantly only at +2.5 °C with +P addition. Based on our results, we posit that phosphorus is an important nutrient in Andean streams that mediates the growth of larval insects. This multiple-stressor experiment suggests that global warming and nutrient enrichment could critically alter the river’s primary productivity and the metabolism of Andean aquatic insects.
Human impacts outpace natural processes in the Amazon Albert, James S; Carnaval, Ana C; Flantua, Suzette G A ...
Science (American Association for the Advancement of Science),
01/2023, Letnik:
379, Številka:
6630
Journal Article
Recenzirano
Amazonian environments are being degraded by modern industrial and agricultural activities at a pace far above anything previously known, imperiling its vast biodiversity reserves and globally ...important ecosystem services. The most substantial threats come from regional deforestation, because of export market demands, and global climate change. The Amazon is currently perched to transition rapidly from a largely forested to a nonforested landscape. These changes are happening much too rapidly for Amazonian species, peoples, and ecosystems to respond adaptively. Policies to prevent the worst outcomes are known and must be enacted immediately. We now need political will and leadership to act on this information. To fail the Amazon is to fail the biosphere, and we fail to act at our peril.
Characterizing dispersal traits can further our ecological understanding of Neotropical stream macroinvertebrate communities, allowing us to test fundamental questions about disturbance and ...functional diversity responses in these systems. We combine observational and experimental approaches to measure short-term colonization of cobbles by stream invertebrates at five headwater streams arrayed along a habitat stability gradient in the Ecuadorian Andes, along with conducting drift and benthic surveys along the same gradient. Cobbles were sampled for benthic macroinvertebrate community composition and basal resource accrual at five time points over the 23-day experimental period. We found that taxonomic richness did not show clear trends across colonization time. Invertebrate community composition in the cobble colonization experiment did not approach the background benthic and drift composition over colonization time. Focal taxa showed variation in their drift and colonization propensities, with no clear relationship to habitat stability. We also found that benthic communities from less stable streams differed greatly between experimental years, highlighting the need to account for intra- and interannual differences in colonization experiments.
Reducing adverse impacts of Amazon hydropower expansion Flecker, Alexander S; Shi, Qinru; Almeida, Rafael M ...
Science (American Association for the Advancement of Science),
02/2022, Letnik:
375, Številka:
6582
Journal Article
Recenzirano
Odprti dostop
Proposed hydropower dams at more than 350 sites throughout the Amazon require strategic evaluation of trade-offs between the numerous ecosystem services provided by Earth's largest and most ...biodiverse river basin. These services are spatially variable, hence collective impacts of newly built dams depend strongly on their configuration. We use multiobjective optimization to identify portfolios of sites that simultaneously minimize impacts on river flow, river connectivity, sediment transport, fish diversity, and greenhouse gas emissions while achieving energy production goals. We find that uncoordinated, dam-by-dam hydropower expansion has resulted in forgone ecosystem service benefits. Minimizing further damage from hydropower development requires considering diverse environmental impacts across the entire basin, as well as cooperation among Amazonian nations. Our findings offer a transferable model for the evaluation of hydropower expansion in transboundary basins.
Life history of benthic faunas of tropical high-altitude cold environments are poorly studied. Here, monthly larval and adult data are presented for
Anomalocosmoecus illiesi
at Saltana Stream in ...Ecuador. In cold conditions throughout the year (6 °C), this species showed an asynchronous and continuous production. Larval density showed two peaks in August and April. All five larval instars were present in most months. Using the size-frequency method an annual rate of secondary production per biomass of 4.8 was calculated. The measured biomass was 785 mg/m
2
.
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